This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The research field focusing on virus-free synthetic vectors intended for therapeutic delivery applications, in particular, using cationic liposome based vectors has recently undergone a renaissance. This is due to the non-immunogenicity of the vectors and the potential of transferring large DNA pieces such as sections of about 1Mbps of human artificial chromosome into cells which is not feasible with viral vectors. However, transfection efficiency (TE;a measure of the expression of an exogenous gene that is transferred into cells) of cationic lipid-DNA complexes (CLDCs), remains low compared to viral vectors and only a significant further increase in our knowledge of the interactions between CLDCs and cells will result in in vitro as well as in vivo optimization of TE.